VorbisComment
The basic document describes LICENSE and COPYRIGHT fields, but is perhaps not clear enough about whether these should be machine-readable:
http://xiph.org/vorbis/doc/v-comment.html
Some proposals for extra field names:
http://reactor-core.org/ogg-tagging.html http://www.gophernet.org/articles/vorbiscomment/
The recommendation at Creative Commons -- we should probably work together to have complementary and interlinked information on the CC and Xiph wikis: